1
JEE Main 2020 (Online) 8th January Morning Slot
+4
-1
The magnifying power of a telescope with tube 60 cm is 5. What is the focal length of its eye piece ?
A
40 cm
B
10 cm
C
30 cm
D
20 cm
2
JEE Main 2020 (Online) 8th January Morning Slot
+4
-1
The critical angle of a medium for a specific wavelength, if the medium has relative permittivity 3 and relative permeability $${4 \over 3}$$ for this wavelength, will be :
A
45°
B
15°
C
30°
D
60°
3
JEE Main 2020 (Online) 7th January Evening Slot
+4
-1
A thin lens made of glass (refractive index = 1.5) of focal length f = 16 cm is immersed in a liquid of refractive index 1.42. If its focal length in liquid is f1 , then the ratio $${{{f_1}} \over f}$$ is closest to the integer :
A
17
B
1
C
9
D
5
4
JEE Main 2020 (Online) 7th January Evening Slot
+4
-1
In a Young's double slit experiment, the separation between the slits is 0.15 mm. in the experiment, a source of light of wavelengh 589 nm is used and the interference pattern is observed on a screen kept 1.5 m away. The separation between the successive bright fringes on the screen is :
A
4.9 mm
B
5.9 mm
C
6.9 mm
D
3.9 mm
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